Numerous types of sailboards are known which are generally adapted to receive on their upper surface a mast adapted to carry a sail and fixed by a mast foot on the board, and foot straps adapted to retain the feet of a user of the board and located rearwardly of the board relative to the mast foot.
It is known that a sailboard receives during its movements on the water dynamic forces of various natures: it receives on its lower surface in contact with the water forces due to the waves, to slapping, to landing after a jump; it also receives on its upper surfaces forces transmitted by the mast foot on the one hand, by the feet of the user retained by the footstrap on the other hand.
These various forces give rise to vibrations of the board. Generally speaking, these vibrations consume energy, requiring a supplemental physical effort on the part of the user of the board, and braking this latter. Moreover, certain of these vibrations, whose frequency corresponds to the frequency of the board itself, give rise to resonance phenomena which aggravate the recited drawbacks.
It is known that the frequency of the sailboard itself depends in particular on the distance separating the mast foot from the footstraps.
It is also known that for a given board, the emplacement of the mast foot is determined, for a given sail, by the position of the center of pressure of the sail, the conditions of navigation, the type and structure of the board. It is not therefore possible to modify this emplacement without risking loss of equilibrium and performance of the board.
Various internal structures of the board have been proposed: they have been able to improve the dynamic behavior of the board only in the case of low frequency vibrations, which are those that the user of the board can overcome at least partially by the action of his leg muscles.
It has also been proposed to mount the foot of the mast in a shock absorber adapted to absorb a portion of the forces transmitted by the latter: such a shock absorber can only function at the level of the amplitude of the vibrations, and not that of the creation of these latter.